Just to inform you in any event of asked to key in/give to someone TAC, please don't release the TAC/key in/give to someone else who asked you. It's a scam. Another thing to avoid is, if you do interested to download/playing games or any other third party apps that you can downloaded from Google Play Store/iOS App Store, please to check further, there is no AUTO-RENEWAL fee incurred for the APPs. Hope this help. Regards.
There are some method you can use :
1) send sms STOP or STOP ALL to *number*
2) send STOP or STOP ALL to 3001
3) send OUT to 3001
4) Block the number via phone.
I hope one of the method help you. TQ